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2248 lines
83 KiB
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<title>Boost Build System</title>
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<img src="../../c++boost.gif" alt="c++boost.gif (8819 bytes)" align=
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<h1>Boost Build System</h1>
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<h2><a name="synopsis">Synopsis</a></h2>
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<p>Boost.Build is a system for large project software construction built
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on Boost.Jam, a descendant of "<a href=
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"http://www.perforce.com/jam/jam.html">Perforce Jam</a>", an open-source
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make replacement<a href="#1">[1]</a>. Key features are:</p>
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<ul>
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<li>A simple target description language</li>
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<li>Build with your choice (or multiple) toolsets from a single command
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invocation</li>
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<li>Build your choice of basic variants (e.g. debug, release,
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profile...) and subvariant modifications (e.g. inlining off) from a
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single command invocation</li>
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<li>``Feature Normalization'' allows target configurations to be
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described independently from the toolset used</li>
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<li>Modular toolset description files allow build instructions for
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different toolsets to be described independently</li>
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<li>Multiple subproject support</li>
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<li>Automatic building of subproject dependencies</li>
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</ul>
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<h2><a name="status">Status</a></h2>
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Boost.Build v1 is a useful, mature system. However, its design and
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structure are not easily adapted to support some of the features we'd
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like to see in the future. To this end, the Boost.Build developers have
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begun work on v2 of Boost.Build, which will be based around this <a href=
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"architecture.html">design document</a>. If you are interested in
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contributing to this effort or you wish to discuss the design of
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Boost.Build, please post inquiries to the <a href=
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"http://groups.yahoo.com/group/jamboost/">jamboost</a> mailing list at
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yahoogroups.
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<p><a href="#design_criteria">Here</a> are some of the design criteria
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that led to these features.</p>
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<h2>Table of Contents</h2>
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<ul>
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<li><a href="#synopsis">Synopsis</a></li>
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<li><a href="#status">Status</a></li>
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<li>
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<a href="#getting_started">Getting Started</a>
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<ul>
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<li><a href="#installing_jam">Installing Boost.Jam</a></li>
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<li><a href="#initiating">Initiating a Build</a></li>
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<li><a href="#setting_variables">Setting Jam Variables</a></li>
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<li><a href="#example_jamfile">An Example Jamfile</a></li>
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<li><a href="#support_files">Support Files</a></li>
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</ul>
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</li>
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<li>
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<a href="#design">Basic Design and Terminology</a>
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<ul>
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<li><a href="#project_subproject">Projects and Subprojects</a></li>
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<li><a href="#targets">Targets</a></li>
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<li><a href="#features">Features and Properties</a></li>
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<li><a href="#variants">Build Variants</a></li>
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<li><a href="#subvariants">Subvariants</a></li>
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<li><a href="#dependents">Dependent Targets</a></li>
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</ul>
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</li>
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<li>
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<a href="#usage">Usage</a>
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<ul>
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<li>
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<a href="#command_line">The Command-Line</a>
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<ul>
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<li><a href="#user_targets">User Targets</a></li>
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<li><a href="#user_globals">Global Variables</a></li>
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</ul>
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</li>
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<li>
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<a href="#subproject_jamfiles">Subproject Jamfiles</a>
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<ul>
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<li><a href="#subproject_rule">The <tt>subproject</tt>
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Rule</a></li>
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<li><a href="#main_targets">Describing Main Targets</a></li>
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<li><a href="#template_targets">Describing Template
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Targets</a></li>
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<li><a href="#stage_targets">Describing Stage Targets</a></li>
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<li><a href="#jamfile_example">Example</a></li>
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</ul>
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</li>
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<li><a href="#feature_description">Feature Descriptions</a></li>
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<li><a href="#variant_description">Variant Descriptions</a></li>
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<li>
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<a href="#toolset_description">Toolset Description Files</a>
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<ul>
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<li><a href="#toolset_example">Example</a></li>
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</ul>
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</li>
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</ul>
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</li>
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<li>
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<a href="#internals">Internals</a>
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<ul>
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<li><a href="#jam_fundamentals">Jam Fundamentals</a></li>
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<li>
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<a href="#core_extensions">Core Jam Extensions</a>
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<ul>
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<li><a href="#variable_quoting">Command-line and Environment
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Variable Quoting</a></li>
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<li><a href="#jambase_replacement">Startup Behavior</a></li>
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<li><a href="#rule_indirection">Rule Indirection</a></li>
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<li><a href="#argument_lists">Argument Lists</a></li>
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<li>
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<a href="#module_support">Module Support</a>
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<ul>
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<li><a href="#module_declaration">Declaration</a></li>
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<li><a href="#module_locals">Variable Scope</a></li>
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<li><a href="#local_rules">Local Rules</a></li>
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<li><a href="#RULENAMES_rule">The <tt>RULENAMES</tt>
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rule</a></li>
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<li><a href="#IMPORT_rule">The <tt>IMPORT</tt>
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rule</a></li>
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<li><a href="#EXPORT_rule">The <tt>EXPORT</tt>
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rule</a></li>
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<li><a href="#CALLER_MODULE_rule">The
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<tt>CALLER_MODULE</tt> rule</a></li>
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</ul>
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</li>
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<li><a href="#local_foreach">Local for Loop Variables</a></li>
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<li><a href="#negative_indexing">Negative Indexing</a></li>
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<li><a href="#BINDRULE">Target Binding Detection</a></li>
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<li><a href="#FAIL_EXPECTED">Return Code Inversion</a></li>
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<li><a href="#NOCARE">Ignoring Return Codes</a></li>
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<li><a href="#RMOLD">Removing outdated targets</a></li>
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<li><a href="#SUBST_rule">The <tt>SUBST</tt> Rule</a></li>
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<li><a href="#JAM_VERSION">The <tt>JAM_VERSION</tt> global
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variable</a></li>
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<li>
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<a href="#debugging_support">Debugging Support</a>
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<ul>
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<li><a href="#BACKTRACE_rule">The BACKTRACE rule</a></li>
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<li><a href="#profiling">Profiling</a></li>
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<li><a href="#parse_debugging">Parser Debugging</a></li>
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<li><a href="#dependency_graph">Dependency Graph
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Output</a></li>
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</ul>
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</li>
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<li><a href="#UPDATE">The <tt>UPDATE</tt> rule and changes to
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command line handling</a></li>
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</ul>
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</li>
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<li><a href="#target_names">Target Names</a></li>
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<li><a href="#internal_globals">Global Variables</a></li>
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</ul>
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</li>
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<li>
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<a href="#design_criteria">Design Criteria</a>
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<ul>
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<li><a href="#assumptions">Assumptions</a></li>
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<li><a href="#requirements">Requirements</a></li>
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</ul>
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</li>
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<li><a href="#footnotes">Footnotes</a></li>
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</ul>
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<h2><a name="getting_started">Getting Started</a></h2>
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<h3><a name="installing_jam">Installing Boost.Jam</a></h3>
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Follow these <a href="index.html#Jam">instructions</a> to acquire a bjam
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executable for your platform. Install it somewhere in your path.
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<h3><a name="initiating">Initiating a Build</a></h3>
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<p>Boost.Build responds to several global variable settings. The easiest
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way to get going is usually to use environment variables, though you can
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also set them on the command-line, using
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<tt>-s</tt><i>VARIABLE_NAME</i><tt>=</tt><i>value</i>. In addition to the
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<a href="index.html#Configuring">toolset configuration variables</a>, you
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can use the <tt>TOOLS</tt> variable to indicate which toolset(s) to build
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with, and the <tt>BUILD</tt> variable to describe how you want things
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built. In many cases it should be sufficient to invoke <code>bjam</code>
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with no variable settings.</p>
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<p>Some example Boost.Jam invocations:</p>
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<table border="1" summary="Sample Jam Invocations=">
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<tr>
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<th>Command Line(s)</th>
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<th>Effects</th>
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</tr>
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<tr>
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<td>
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<pre>
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bjam -sTOOLS=gcc my_target
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</pre>
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</td>
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<td>default (debug) <tt><a href="#build">BUILD</a></tt> of
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<tt>my_target</tt>with GCC</td>
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</tr>
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<tr>
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<td>
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<pre>
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bjam -sTOOLS="msvc gcc"
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</pre>
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</td>
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<td>default-build <tt>all</tt> with msvc and gcc</td>
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</tr>
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<tr>
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<td>
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<pre>
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set TOOLS=msvc
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bjam
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</pre>
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</td>
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<td>Set an NT environment variable to always build with MSVC<br>
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default-build <tt>all</tt>.</td>
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</tr>
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<tr>
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<td>
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<pre>
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bjam "-sBUILD=release <debug-symbols>on"
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</pre>
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</td>
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<td>release build with debug symbols of <tt>all</tt> using default
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<tt><a href="#tools">TOOLS</a></tt></td>
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</tr>
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<tr>
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<td>
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<pre>
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bjam -sBUILD="debug release"
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</pre>
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</td>
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<td>debug and release build <tt>all</tt>.</td>
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</tr>
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<tr>
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<td><code>set TOOLS=msvc<br>
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bjam -sBUILD="<cxxflags>/G6"<br>
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</code></td>
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<td>Set an NT environment variable to always build with MSVC<br>
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default-build <tt>all</tt>, adding a compiler command line
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switch</td>
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</tr>
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<tr>
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<td><code>set TOOLS=msvc gcc<br>
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bjam -sBUILD="<msvc><*><cxxflags>/G6"<br>
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</code></td>
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<td>Set an NT environment variable to always build with MSVC and
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GCC<br>
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default-build <tt>all</tt>, adding a MSVC-specific compiler command
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line switch</td>
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</tr>
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</table>
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<h3><a name="setting_variables">Setting Jam Variables</a></h3>
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<p>The "<tt>-s</tt>" options in the command lines above are passing
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variable settings to the build system. There are actually three ways to
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do that:</p>
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<ul>
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<li>
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Jam picks up variable settings from your environment by default, so
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you can set them there:
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<blockquote>
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<pre>
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> <a href="#build">BUILD</a>="debug release" <i># assuming Unix</i>
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> export <a href="#build">BUILD</a>
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> bjam ...
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</pre>
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</blockquote>
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This approach can be OK for quick-and-dirty tests, but environment
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variable settings tend to be unstable and non-uniform across users
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and machines, so it's best not to rely on the environment much.
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</li>
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<li>Explicitly on the command-line, with the "<tt>-s</tt>" option.</li>
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<li>Directly in Jam code. A project's <a href="#jamrules">Jamrules</a>
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file is a convenient place to make global settings.</li>
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</ul>
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<h3><a name="example_jamfile">An Example Jamfile</a></h3>
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Here is an example of a simple subproject Jamfile. In this example, it is
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assumed that the user has set <tt>BOOST_ROOT</tt>, either as an
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environment variable, on the command-line or in the project's <tt><a
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href="#jamrules">Jamrules</a></tt> file:
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<blockquote>
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<pre>
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subproject foo/bar/baz ; # path to here from project root
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# A static library called 'baz'
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lib baz : baz1.cpp baz2.cpp # C++ sources
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parser/src/baz4.ll # Lex->C++ sources
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parser/src/baz5.yy # Yacc->C++ sources
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: <include>$(BOOST_PARENT_DIRECTORY) # Put boost in #include path
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;
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# An executable called 'test'
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exe test : <lib>baz # use the 'baz' library
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baz_test.cpp # C++ source
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: <include>$(BOOST_ROOT)
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;
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</pre>
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</blockquote>
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<p>That's it! The build system takes care of the rest. If the you want to
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be able to build all subprojects from the project root directory, you can
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add a Jamfile at the root:</p>
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<blockquote>
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<pre>
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project-root ; # declare this to be the project root directory
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# Read subproject Jamfiles
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subinclude foo/bar/baz <font color="#7F7F7F">foo/bar/...</font> ;
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<font color="#7F7F7F">subinclude a/b/c ...</font> ; # more subincludes
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</pre>
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</blockquote>
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<h3><a name="support_files">Support Files</a></h3>
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<p>To use the build system, the following must be located in your
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project's root directory, or in a directory specified in the
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<tt>BOOST_BUILD_PATH</tt> variable. It is usually convenient to specify
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the <tt>BOOST_BUILD_PATH</tt> in your project's <a href=
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"#jamrules">Jamrules</a> file. The <a href="../../Jamrules">Boost
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Jamrules</a> file shows an example.</p>
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<table border="1" summary="Support Files">
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<tr>
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<th>Filename(s)</th>
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<th>Meaning</th>
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</tr>
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<tr>
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<td><i>toolset</i><tt>-tools.jam</tt></td>
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<td>Feature-to-command-line mapping for <i>toolset</i>.</td>
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</tr>
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<tr>
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<td><tt>features.jam</tt></td>
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<td>Abstract toolset feature descriptions.</td>
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</tr>
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<tr>
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<td><tt>boost-base.jam</tt></td>
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<td>Boost build system-specific rule definitions.</td>
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</tr>
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<tr>
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<td><tt>unit-tests.jam</tt></td>
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<td>Unit tests and assertions for boost Jam code.</td>
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</tr>
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</table>
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The <tt>boost-base.jam</tt> file is temporary, and will eventually be
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compiled into our Jam executable.
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<h2><a name="design">Basic Design and Terminology</a></h2>
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This section gives an overview of the way that the system works,
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outlining the system's capabilities and overall design. It also
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introduces the terminology and concepts necessary to understand the
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sections on writing Jamfiles and command-line invocations.
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<h3><a name="project_subproject">Projects and Subprojects</a></h3>
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<p>A <b>project</b> is a source directory tree containing at least one
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<tt>Jamfile</tt>. The root directory of the project is known as the
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<b>project root</b>. <a name="jamrules">The</a> root directory of a
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project may contain a <tt>Jamrules</tt> file, which contains
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project-specific Jam code. If the <tt>Jamrules</tt> file is not present
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when Jam is invoked, a warning will be issued.</p>
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<p>Subdirectories containing <tt>Jamfile</tt>s are called <b>subproject
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directories</b>. Each such <tt>Jamfile</tt> describes a
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<b>subproject</b>.</p>
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<p>The <b>build system installation directory</b> is a directory
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containing Jam files describing compilers and build variants. The
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installation directory can be specified implicitly by setting the
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variable <tt>BOOST_BUILD_PATH</tt>. This lists a set of directories to
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search for the files comprising the build system. If the installation
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directory is not specified, it is the same as the project root, and
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<tt>BOOST_BUILD_PATH</tt> is set to include that directory.</p>
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<h3><a name="targets">Targets</a></h3>
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<p>Each <tt>Jamfile</tt> describes one or more <b>main targets</b>.</p>
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<p>Each main target is an abstract description of one or more <b>built
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targets</b> which are expressions of the corresponding main target under
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particular compilers and build variants. Intermediate files such as
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<tt>.o</tt>/<tt>.obj</tt> files generated by compiling <tt>.cpp</tt>
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files as a consequence of building a main target are also referred to as
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built targets. The term <b>build directory tree</b> refers to the
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location of built target files.</p>
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<ul>
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<li>By default, the build directory tree is overlaid with the project
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directory tree, with targets generated into a subtree rooted at the
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<tt>bin</tt> subdirectory of each subproject directory (the name of
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this directory can be customized by changing the <tt>BIN_DIRECTORY</tt>
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variable.</li>
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<li><a name="all_locate_target">If the variable
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<tt>ALL_LOCATE_TARGET</tt> is set</a>, it specifies an alternate build
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directory tree whose structure mirrors that of the project. In this
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case, built targets of a subproject are generated into the
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corresponding directory of the build directory tree.</li>
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</ul>
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|
For each main target, there is a corresponding location in the build
|
|
directory tree known as the target's <b>build root</b>, where all
|
|
intermediate and final targets resulting from that main target are
|
|
located.
|
|
|
|
<h3><a name="features">Features and Properties</a></h3>
|
|
|
|
<p>A <b>feature</b> is a normalized (toolset-independent) description of
|
|
an individual build parameter, such as whether inlining is enabled. Each
|
|
feature usually corresponds to a command-line option of one or more build
|
|
tools. Features come in four varieties:</p>
|
|
|
|
<ol>
|
|
<li><b>Simple features</b> can take on any of several predetermined
|
|
values. For example, the feature <tt>optimization</tt> might take one
|
|
of the values <tt>off</tt>, <tt>speed</tt>, or <tt>space</tt>. Simple
|
|
features have a default value. The key aspect of simple features is
|
|
that they are assumed to affect link compatibility: object files
|
|
generated with different values for a simple feature are generated into
|
|
a separate directories, and (with a few exceptions) main targets
|
|
generated with different values won't be linked together.</li>
|
|
|
|
<li><b>Free features</b> can either be single-valued, as above, or may
|
|
take on any number of user-specified values simultaneously. For
|
|
example, the <tt>define</tt> feature for a release build might have the
|
|
values <tt>NDEBUG</tt> and <tt>BOOST_RELEASE_BUILD</tt>. Free features
|
|
are assumed not to affect link compatibility.</li>
|
|
|
|
<li><b>Path features</b> are free features whose values describe paths
|
|
which may be relative to the subproject (such as linked libraries or
|
|
<tt>#include</tt> search directories). The build system treats the
|
|
values of these features specially to ensure that they are interpreted
|
|
relative to the subproject directory regardless of the directory where
|
|
Jam was invoked.</li>
|
|
|
|
<li><b>Dependency features</b> are path features whose values describe
|
|
a dependency of built targets. For example, an external library might
|
|
be specified with a dependency-feature: if the library is updated, the
|
|
target will be updated also. The <tt><library-file></tt> feature
|
|
works this way <a href="#2">[2]</a>.</li>
|
|
</ol>
|
|
|
|
<p>A feature-value pair is known as a <b>build property</b>, or simply
|
|
<b>property</b>. The prefixes <i>simple</i>, <i>free</i>, <i>path</i>,
|
|
and <i>dependency</i> apply to properties in an analogous way to
|
|
features.</p>
|
|
|
|
<h3><a name="variants">Build Variants</a></h3>
|
|
|
|
<p>A build variant, or simply <b>variant</b> is a named set of build
|
|
properties describing how targets should be built. Typically you'll want
|
|
at least two separate variants: one for debugging, and one for your
|
|
release code.</p>
|
|
|
|
<p>Built targets for distinct build variants and toolsets are generated
|
|
in separate parts of the build directory tree, known as the <b>variant
|
|
directories</b>. For example, a (sub)project with main targets
|
|
<tt>foo</tt> and <tt>bar</tt>, compiled with both GCC and KAI for
|
|
<tt>debug</tt> and <tt>release</tt> variants might generate the following
|
|
structure (target directories in <b>bold</b>).</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
bin
|
|
+-foo <font color="#7F7F7F"><--- foo's build root</font>
|
|
| +-gcc
|
|
| | +-<b>debug</b>
|
|
| | `-<b>release</b>
|
|
| `-kai
|
|
| +-<b>debug</b>
|
|
| `-<b>release</b>
|
|
`-bar <font color="#7F7F7F"><--- bar's build root</font>
|
|
+-gcc
|
|
| +-<b>debug</b>
|
|
| `-<b>release</b>
|
|
`-kai
|
|
+-<b>debug</b>
|
|
`-<b>release</b>
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p>The properties constituting a variant may differ according to toolset,
|
|
so <tt>debug</tt> may mean a slightly different set of properties for two
|
|
different compilers.</p>
|
|
|
|
<h3><a name="subvariants">Subvariants</a></h3>
|
|
|
|
<p>When a target is built with <i>simple</i> properties that don't
|
|
exactly match those specified in a build variant, the non-matching
|
|
features are called <b>subvariant features</b> and the target is located
|
|
in a <b>subvariant directory</b> beneath the directory of the base
|
|
variant. This can occur for two reasons:</p>
|
|
|
|
<ol>
|
|
<li>
|
|
Some features are only relevant to certain compilers. When relevant
|
|
simple features have no value specified in the build variant, a value
|
|
must be chosen. Even when the default value is used, the target is
|
|
generated into a subvariant directory. For example, the
|
|
<tt>runtime-link</tt> feature may be unspecified in the
|
|
<tt>debug</tt> variant, but relevant to MSVC. In that case, a
|
|
fragment of the target tree might look like:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
bin
|
|
+-foo <font color="#7F7F7F"><--- foo's build root</font>
|
|
| +-msvc
|
|
| | +-debug
|
|
. . . `-<b>runtime-link-dynamic</b>
|
|
. . .
|
|
</pre>
|
|
</blockquote>
|
|
Because the default value of <tt>runtime-link</tt> is
|
|
<tt>dynamic</tt>, when the <tt>debug</tt> variant is requested, the
|
|
<tt>runtime-link-dynamic</tt> subvariant of foo is built.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>
|
|
It is possible to request (either on the command-line, or as part of
|
|
a main target description) that particular subvariants be built. For
|
|
example, it may be desirable to generate builds that link to the
|
|
runtime both statically <i>and</i> dynamically. In that case, both
|
|
subvariant directories in the example above would be generated:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
bin
|
|
+-foo <font color="#7F7F7F"><--- foo's build root</font>
|
|
| +-msvc
|
|
| | +-debug
|
|
. . . +-<b>runtime-link-dynamic</b>
|
|
. . . `-<b>runtime-link-static</b>
|
|
. . .
|
|
</pre>
|
|
</blockquote>
|
|
</li>
|
|
</ol>
|
|
In no case will targets be built directly into
|
|
<tt>bin/foo/msvc/debug</tt>, since the <tt>debug</tt> variant doesn't
|
|
include the <tt>runtime-link</tt> feature, which is relevant to MSVC.
|
|
|
|
<p>When a subvariant includes multiple subvariant features, targets are
|
|
built into a subvariant directory whose path is determined by
|
|
concatenating the properties sorted in order of their feature names. For
|
|
example, the borland compiler, which uses different libraries depending
|
|
on whether the target is a console or GUI program, might create the
|
|
following structure for a DLL:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
bin
|
|
+-foo <font color="#7F7F7F"><--- foo's build root</font>
|
|
| +-msvc
|
|
| | +-debug
|
|
| | | +-runtime-link-dynamic
|
|
| | | | +-<b>user-interface-console</b>
|
|
| | | | `-<b>user-interface-gui</b>
|
|
. . . `-runtime-link-static
|
|
. . . +-<b>user-interface-console</b>
|
|
. . . `user-interface-gui
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p>Any configuration of properties for which a target is built, whether
|
|
base variant or subvariant, is known as a <b>build configuration</b>, or
|
|
simply a <b>build</b>.</p>
|
|
|
|
<h3><a name="dependents">Dependent Targets</a></h3>
|
|
|
|
<p>When a main target depends on the product of a second main target (as
|
|
when an executable depends on and links to a static library), each build
|
|
configuration of the dependent target is depends on the
|
|
<i>corresponding</i> build of the dependency. Because only simple
|
|
features participate in build identity, the dependent and dependency
|
|
targets may have completely different free features. This puts the onus
|
|
on the user for ensuring link-compatibility when certain free properties
|
|
are used. For example, when <tt>assert()</tt> is used in header files,
|
|
the preprocessor symbol <tt>NDEBUG</tt> can impact link-compatibility of
|
|
separate compilation units. This danger can be minimized by encapsulating
|
|
such feature differences inside of build variants.</p>
|
|
|
|
<h2><a name="usage">Usage</a></h2>
|
|
|
|
<p>This section describes how to start a build from the command-line and
|
|
how to write project and subproject Jamfiles. It also describes the other
|
|
files written in the Jam language: build-tool specification files,
|
|
feature descriptions files.</p>
|
|
|
|
<h3><a name="command_line">The Command Line</a></h3>
|
|
|
|
<p>This section describes in detail how the build system can be
|
|
invoked.</p>
|
|
|
|
<h4><a name="user_targets">User Targets</a></h4>
|
|
|
|
<p>The Jam command line ends with an optional list of target names; if no
|
|
target names are supplied, the built-in pseudotarget <tt>all</tt> is
|
|
built. In a large project, naming targets can be dicey because of
|
|
collisions. Jam uses a mechanism called <a href="#grist">grist</a> to
|
|
distinguish targets that would otherwise have the same name. Fortunately,
|
|
you won't often have to supply grist at the command-line. When you
|
|
declare a main target, a Jam pseudotarget of the same name is created
|
|
which depends on <i>all</i> of the subvariants requested for your
|
|
invocation of the build system. For example, if your subproject
|
|
declares:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
exe my_target : my_source1.cpp my_source2.c ;
|
|
</pre>
|
|
</blockquote>
|
|
and you invoke Jam with <tt>-sBUILD="debug release" my_target</tt>,
|
|
you will build both the debug and release versions of <tt>my_target</tt>.
|
|
|
|
|
|
<p>These simple, ungristed names are called <b>user targets</b>, and are
|
|
only available for the subproject where Jam is invoked. That way, builds
|
|
from the top level (which may include many Jamfiles through the
|
|
subinclude rule) and builds of library dependencies (which may live in
|
|
other subprojects), don't collide. If it is necessary to refer more
|
|
explicitly to a particular target from the command-line, you will have to
|
|
add ``grist''. Please see <a href="#target_names">this section</a> for a
|
|
more complete description of how to name particular targets in a
|
|
build.</p>
|
|
|
|
<h4><a name="user_globals">Global Variables</a></h4>
|
|
|
|
<p>This is a partial list of global variables that can be set on the
|
|
command-line. Of course you are free to write your own Jam rules which
|
|
interpret other variables from the command-line. This list just details
|
|
some of the variables used by the build system itself. Note also that if
|
|
you don't like the default values you can override them in your project's
|
|
<tt><a href="#jamrules">Jamrules</a></tt> file.</p>
|
|
|
|
<table border="1" summary="User Globals">
|
|
<tr>
|
|
<th>Variable <!-- <th>Meaning --></th>
|
|
|
|
<th>Default</th>
|
|
|
|
<th>Example</th>
|
|
|
|
<th>Notes</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td rowspan="2"><tt><a name="tools">TOOLS</a></tt>
|
|
<!-- <td rowspan="2">Toolsets to build with --></td>
|
|
|
|
<td rowspan="2">Platform-dependent</td>
|
|
|
|
<td><tt>"-sTOOLS=gcc msvc"</tt></td>
|
|
|
|
<td>build with gcc and msvc</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><tt>-sTOOLS=gcc</tt></td>
|
|
|
|
<td>build with gcc</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td rowspan="4"><tt><a name="build">BUILD</a></tt>
|
|
<!-- <td rowspan="4">Build configuration (see -->
|
|
<!-- <a href="#default_build">here</a>). -->
|
|
</td>
|
|
|
|
<td rowspan="4"><tt>debug</tt></td>
|
|
|
|
<td><tt>-sBUILD=release</tt></td>
|
|
|
|
<td>build the <tt>release</tt> variant</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><tt>"-sBUILD=debug release"</tt></td>
|
|
|
|
<td>build both <tt>debug</tt> and <tt>release</tt> variants</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><tt>"-sBUILD=<optimization>speed"</tt></td>
|
|
|
|
<td>build a subvariant of the default variant (<tt>debug</tt>) with
|
|
optimization for speed.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><tt>"-sBUILD=debug release
|
|
<runtime-link>static/dynamic"</tt></td>
|
|
|
|
<td>build subvariants of the debug and release variants that link to
|
|
the runtime both statically and dynamically.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><tt>ALL_LOCATE_TARGET</tt>
|
|
<!-- <td>Alternate location for built targets (see <a -->
|
|
<!-- href="#all_locate_target">here</a>) -->
|
|
</td>
|
|
|
|
<td><i>empty</i></td>
|
|
|
|
<td><tt>-sALL_LOCATE_TARGET=~/build</tt></td>
|
|
|
|
<td>Generate all build results in the <tt>build</tt> subdirectory of
|
|
the user's home directory (UNIX).</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<h3><a name="#subproject_jamfiles">SubProject Jamfiles</a></h3>
|
|
This section describes how to write a Jamfile for a subproject.
|
|
|
|
<h4><a name="subproject_rule">The <tt>subproject</tt> rule</a></h4>
|
|
|
|
<p>A subproject's Jamfile begins with an invocation of the
|
|
<tt>subproject</tt> rule that specifies the subproject's location
|
|
relative to the top of the project tree:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
subproject <i>path-from-top</i> ;
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p>The <tt>subproject</tt> rule tells the build system where to place
|
|
built targets from the subproject in case <tt>ALL_LOCATE_TARGET</tt> is
|
|
used to specify the build directory tree. If there is a Jamfile in the
|
|
project root directory, you should use the <tt>project-root</tt> rule
|
|
instead:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
project-root ;
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<h4><a name="main_targets">Describing Main Targets</a></h4>
|
|
|
|
<p>A main target is described using the following syntax:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
<i>target-type</i> <i>name</i> : <i>sources</i>
|
|
[ : <i>requirements</i> [ : <i><a href=
|
|
"#default_build">default-BUILD</a></i> ] ] ;
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<ul>
|
|
<li><i>target-type</i> may be one of <tt>exe</tt>, <tt>lib</tt>,
|
|
<tt>dll</tt>, <tt>stage</tt> or <tt>template</tt>. These are actually
|
|
names of Jam rules. Additional main target rules are possible; see
|
|
<tt><a href="../../status/Jamfile">status/Jamfile</a></tt> or <tt><a
|
|
href=
|
|
"../../libs/python/build/Jamfile">libs/python/build/Jamfile</a></tt>
|
|
for examples.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><i>name</i> specifies the name of the main target, multiple targets
|
|
with the same name are allowed but only if they are of different types.
|
|
Normally this is not the name of the final target file generated. The
|
|
target file name depends on the type of target which controls how the
|
|
base target name is renamed to conform to platform conventions. For
|
|
<tt>exe</tt>s the name might be the same or <tt>*.exe</tt>. For
|
|
<tt>lib</tt>s the name might be <tt>*.lib</tt> or <tt>lib*.a</tt>. And
|
|
for <tt>dll</tt>s the name might be <tt>*.dll</tt> or <tt>lib*.so</tt>.
|
|
For platform specific naming consult the <tt><a href=
|
|
"allyourbase.jam">allyourbase.jam</a></tt> file in the build
|
|
system.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><i>sources</i> is a list of paths to source files and dependency
|
|
targets. A dependency target path is preceded by
|
|
<tt><template></tt>, <tt><lib></tt>, <tt><dll></tt>,
|
|
or <tt><exe></tt>, and the final path component specifies the
|
|
name of a main target in a Jamfile located in the directory given by
|
|
the initial path components. Paths may be absolute or relative. The
|
|
type of dependency is also used to decide how to link to it when
|
|
needed. Specifying a <tt><lib></tt> indicates the use of static
|
|
linking, as opposed to specifying a <tt><dll></tt> which uses
|
|
dynamic linking. For example in Unix static linking will be done
|
|
directly, and dynamic linking with the common "<tt>-l</tt>" liker flag
|
|
and use of <tt>LD_LIBRARY_PATH</tt>.<br>
|
|
<br>
|
|
<b>NOTE:</b> It is important to match up the type of source dependency
|
|
with the same type the dependency is built as. Trying to specify a
|
|
source dependency of <tt><lib></tt> when the target is defined as
|
|
a <tt><dll></tt> will cause an error.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>
|
|
<i><a name="target_requirements">requirements</a></i> specifies the
|
|
build properties intrinsic to the target. Requirements are given as
|
|
sets of optionally-<b>qualified build properties</b>:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
[[<<i>compiler</i>>]<<i>variant</i>>]<<i>feature</i>><i>value</i>
|
|
</pre>
|
|
</blockquote>
|
|
<tt><<i>compiler</i>></tt> and <tt><<i>variant</i>></tt>,
|
|
if supplied, can be used to restrict the applicability of the
|
|
requirement. Either one may be replaced by <tt><*></tt>, which
|
|
is the same as omitting it.
|
|
|
|
<p>The system checks that simple feature requirements are not
|
|
violated by explicit subvariant build requests, and will issue a
|
|
warning otherwise. Free features specified as requirements are simply
|
|
added to each corresponding build configuration.<br>
|
|
<br>
|
|
</p>
|
|
</li>
|
|
|
|
<li>
|
|
<i><a name="default_build">default-BUILD</a></i> specifies the
|
|
configurations that should be built if the <tt><a href=
|
|
"#build">BUILD</a></tt> variable is not otherwise specified. Any
|
|
elements not beginning with ``<tt><</tt>...<tt>></tt>'' refer
|
|
to build variants. Other elements use the same syntax as the <a href=
|
|
"#target_requirements">requirements</a> described above, except that
|
|
multiple values may be specified for a simple feature by separating
|
|
them with a slash, forming (qualified) <b>multi-valued
|
|
properties</b>:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
[[<<i>compiler</i>>]<<i>variant</i>>]<<i>feature</i>><i>value1</i>[/<i>value2</i>...]
|
|
</pre>
|
|
</blockquote>
|
|
When multiple values are specified, it causes <i>all</i> the implied
|
|
configurations to be built by default. It is also possible to prevent
|
|
any default builds from occurring on this target by using
|
|
<code><suppress>true</code> . This suppresses any local
|
|
targets, either implicit or explicit, from building. But, this does
|
|
not prevent implied targets as required by a dependency by another
|
|
target to this one from being built. This is useful, for example, for
|
|
defining a set of libraries generically and having them built only
|
|
when another target like an exe is built. Such use might look like:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
lib basic : basic.cpp : : <suppress>true ;<br>
|
|
<br>
|
|
exe test : test.cpp <lib>basic ;<br>
|
|
</pre>
|
|
</blockquote>
|
|
With that the <tt>basic</tt> library will only be built when the
|
|
<tt>test</tt> executable is built, and only the variations required
|
|
by the executable will be built.<br>
|
|
</li>
|
|
</ul>
|
|
|
|
<p><b>NOTE:</b> for simple features in both <i><a href=
|
|
"#target_requirements">requirements</a></i> and <i><a href=
|
|
"#default_build">default-BUILD</a></i>, more-specific qualification
|
|
overrides less-specific.</p>
|
|
|
|
<h4><a name="template_targets">Describing Template Targets</a></h4>
|
|
|
|
<p>Template targets provide a way to handle commonalities between
|
|
projects targets. They have the same form as <a href="#main_targets">main
|
|
targets</a> but do not initiate build requests. A target that lists a
|
|
template as a dependency inherits all the settings from the template,
|
|
i.e. the templates sources, requirements and default build settings will
|
|
be added to the targets settings. Paths mentioned in a template
|
|
definition are always relative to the subdirectory of the Jamfile
|
|
containing the templates definition, regardless of the subdirectory of
|
|
the dependent main target. Typically a project will have at least one
|
|
template target that handles defines, include paths and additional
|
|
compiler flags common to all targets in the project.</p>
|
|
|
|
<h4><a name="stage_targets">Describing Stage Targets</a></h4>
|
|
|
|
<p>Stage targets are a special kind of target that don't build a single
|
|
file but to a collection of files. The goal is to create a directory
|
|
which is composed of the various files that other targets generate, or
|
|
individual files. When built a stage target creates a directory with the
|
|
same name as the target, and copies the dependent files to it. The form
|
|
of the target is the same as that of <a href="#main_targets">main
|
|
targets</a> with some differences...</p>
|
|
|
|
<ul>
|
|
<li><i>target-type</i> is <tt>stage</tt>. See <tt><a href=
|
|
"../../libs/regex/build/Jamfile">libs/regex/build/Jamfile</a></tt> for
|
|
an example.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><i>Name</i> specifies the name of the stage and is the name of the
|
|
directory created.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><i>sources</i> is the same as main targets and one can list both
|
|
generated targets like <tt><exe>test_exe</tt> and individual
|
|
files, but not template targets.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>
|
|
<i>Requirements</i> the build properties specified are used as with
|
|
main targets. But one additional type of requirement is possible:
|
|
<tt><tag></tt>... A tag specifies how to "augment" the names of
|
|
the copied files. This is needed to distinguish the various files if
|
|
your collecting different builds of the same targets. The syntax is:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
<tag><<i>feature|variant</i>><i>value</i>
|
|
</pre>
|
|
</blockquote>
|
|
<br>
|
|
If the <tt><i>feature</i></tt> or <tt><i>variant</i></tt> is present
|
|
for the a target the file for that target is renamed to include the
|
|
given <tt><i>value</i></tt> between the basename and the suffix. Two
|
|
special <tt>tag</tt>s, <tt><tag><prefix></tt> and
|
|
<tt><tag><postfix></tt>, let one prepend and append a
|
|
value to the "augmentation" respectively.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><i>default-BUILD</i> acts in the same manner as a main target.<br>
|
|
</li>
|
|
</ul>
|
|
|
|
<h4><a name="jamfile_example">Example</a></h4>
|
|
|
|
<p>This artificially complex example shows how two executables called
|
|
"foo" and "fop" might be described in a Jamfile. All common settings are
|
|
factored out in the templates "base" and "executable". Foo is composed of
|
|
the sources <tt>./foo.cpp</tt> and <tt>./src/bar.cpp</tt> (specified
|
|
relative to the directory in which the Jamfile resides). Fop only has one
|
|
sourcefile <tt>./fop.cpp</tt>. Both executables link against the built
|
|
target which results from building the target <tt>baz</tt> as described
|
|
in <tt>../bazlib/Jamfile</tt>.</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
template base :
|
|
## <a href="#target_requirements">Requirements</a> ##
|
|
: <include>../bazlib/include
|
|
<define>BUILDING_FOO=1
|
|
<release><define>FOO_RELEASE
|
|
<msvc><*><define>FOO_MSVC
|
|
<msvc><release><define>FOO_MSVC_RELEASE
|
|
<gcc><*><optimization>off
|
|
<gcc><release><optimization>space
|
|
<threading>multi
|
|
<sysinclude>/usr/local/foolib/include
|
|
|
|
## <a href="#default_build">default-BUILD</a> ##
|
|
: debug release
|
|
<debug><runtime-link>static/dynamic
|
|
;
|
|
|
|
template executable : <template>base <lib>../bazlib/baz ;
|
|
|
|
exe foo : <template>executable foo.cpp src/bar.cpp ;
|
|
|
|
exe fop : <template>executable fop.cpp ;
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p>The <a href="#target_requirements">requirements</a> section:</p>
|
|
|
|
<ul>
|
|
<li>Adds <tt>../bazlib/include</tt> to the <tt>#include</tt> path</li>
|
|
|
|
<li>Sets the preprocessor symbol <tt>BUILDING_FOO</tt> to
|
|
<tt>1</tt></li>
|
|
|
|
<li>In the <tt>release</tt> builds, <tt>#define</tt>s
|
|
<tt>FOO_RELEASE</tt>.</li>
|
|
|
|
<li>When built with MSVC, <tt>#define</tt>s <tt>FOO_MSVC</tt>.</li>
|
|
|
|
<li>In <tt>release</tt> variants built with MSVC, <tt>#define</tt>s
|
|
<tt>FOO_MSVC_RELEASE</tt>.</li>
|
|
|
|
<li>Most builds under GCC have optimization turned off, but...</li>
|
|
|
|
<li>...GCC <tt>release</tt> builds require optimization for space.</li>
|
|
|
|
<li>Requires multithread support on compilers where it's relevant.</li>
|
|
|
|
<li>Adds <tt>/usr/local/foolib/include</tt> to the <tt>#include
|
|
<*></tt> path</li>
|
|
</ul>
|
|
|
|
<p>The <a href="#default_build">default-BUILD</a> section:</p>
|
|
|
|
<ul>
|
|
<li>specifies that <tt>debug</tt> and <tt>release</tt> base variants
|
|
are built by default.</li>
|
|
|
|
<li>on compilers where the feature is relevant, requests both
|
|
statically- and dynamically-linked subvariants of the debug
|
|
variant.</li>
|
|
</ul>
|
|
|
|
<h3><a name="feature_description">Feature Descriptions</a></h3>
|
|
|
|
<p>Features are described by stating the feature type (simple features
|
|
are specified with "<tt>feature</tt>"), followed by the feature name. An
|
|
optional second argument can be used to list the permissible values of
|
|
the feature. Examples can be found in <a href=
|
|
"features.jam">features.jam</a>.</p>
|
|
|
|
<h3><a name="variant_description">Variant Descriptions</a></h3>
|
|
|
|
<p>Variants are described with the following syntax:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
variant <i>name</i> : [<<i>toolset-name</i>>]<<i>feature</i>>value... ;
|
|
</pre>
|
|
</blockquote>
|
|
The <tt>variant</tt> rule specifies the list of properties comprising a
|
|
variant. Properties may be optionally qualified with a toolset name,
|
|
which specifies that the property applies only to that toolset. One or
|
|
more parent variants may be specified to inherit the properties
|
|
from those parent(s). For inherited properties precedence is given
|
|
on a left to right order, making the immediate properties override those
|
|
in the parent(s). This can be used to great effect for describing global
|
|
properties that are shared amongst various variants, and therefore
|
|
targets. For example:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
variant my-globals : <rtti>off ;
|
|
|
|
variant my-debug : my-globals debug ;
|
|
|
|
variant my-release : my-globals release ;
|
|
</pre>
|
|
</blockquote>
|
|
More examples can be found in <a href="features.jam">features.jam</a>.
|
|
|
|
<h3><a name="toolset_description">Toolset Description Files</a></h3>
|
|
|
|
<p>Toolset descriptions are located in the project's root directory, or a
|
|
directory specified by <tt>BOOST_BUILD_INSTALLATION</tt>, which may be
|
|
set in a <tt>Jamfile</tt> or the project's <tt><a href=
|
|
"#jamrules">Jamrules</a></tt> file. Each file is called
|
|
<i>toolset-name</i><tt>-tools.jam</tt>, where <i>toolset-name</i> is the
|
|
name of the toolset. The toolset description file has two main jobs:</p>
|
|
|
|
<ol>
|
|
<li>
|
|
redefine the following rules:
|
|
|
|
<ul>
|
|
<li><tt>Link-action</tt> - links an executable from objects and
|
|
libraries</li>
|
|
|
|
<li><tt>Archive-action</tt> - links a static library from object
|
|
files</li>
|
|
|
|
<li><tt>C++-action</tt> - compiles a 'C++' file into an object
|
|
file</li>
|
|
|
|
<li><tt>Cc-action</tt> - compiles a 'C' file into an object
|
|
file</li>
|
|
</ul>
|
|
These rules should simply invoke the action part of a rule whose name
|
|
is uniquely defined for the toolset. For example,
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule C++-action
|
|
{
|
|
msvc-C++-action $(<) : $(>) ;
|
|
}
|
|
|
|
actions msvc-C++-action
|
|
{
|
|
cl -nologo -GX -c -U$(UNDEFS) -D$(DEFINES) $(CFLAGS) $(C++FLAGS) -I$(HDRS) -I$(STDHDRS) -Fo$(<) -Tp$(>)
|
|
}
|
|
|
|
</pre>
|
|
</blockquote>
|
|
Note that <tt>Link-action</tt> may require special care: on platforms
|
|
where the global variable <tt>gEXPORT_SUFFIX(DLL)</tt> is defined
|
|
(e.g. Windows), the first argument may have two elements when linking
|
|
a shared library. The first is the shared library target, and the
|
|
second is the import library target, with suffix given by
|
|
<tt>$(gEXPORT_SUFFIX(DLL))</tt>. It will always have a third argument
|
|
which is either ``<tt>EXE</tt>'' or ``<tt>DLL</tt>''. This can be
|
|
used to dispatch to different actions for linking DLLs and EXEs if
|
|
necessary, but usually it will be easier to take advantage of the
|
|
special <tt><target-type></tt> feature, which will have the
|
|
same value using the <tt>flags</tt> rule described below.
|
|
</li>
|
|
|
|
<li>
|
|
Translate build settings given in the global
|
|
<tt>gBUILD_PROPERTIES</tt> variable into something that can be used
|
|
by the toolset. The build system provides the <tt>flags</tt> rule to
|
|
help translate build properties into elements of global variables
|
|
which are later attached to targets so that they can affect the build
|
|
actions. The <tt>flags</tt> rule is used as follows:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
flags <i>toolset variable condition</i> [: <i>value</i>...]
|
|
</pre>
|
|
</blockquote>
|
|
The parameters are:
|
|
|
|
<ul>
|
|
<li><i>toolset</i> - the name of the toolset</li>
|
|
|
|
<li><i>variable</i> - the name of a global variable which can be
|
|
used to carry information to a command-line</li>
|
|
|
|
<li>
|
|
<i>condition</i> - one one or more elements in the following
|
|
forms:
|
|
|
|
<ol>
|
|
<li>a property-set of the form:
|
|
<tt><<i>feature</i>><i>value</i></tt>[<tt>/<<i>feature</i>>
|
|
<i>value</i></tt>...]</li>
|
|
|
|
<li><tt><<i>feature</i>></tt></li>
|
|
</ol>
|
|
</li>
|
|
|
|
<li><i>values</i> - anything</li>
|
|
</ul>
|
|
|
|
<p>Semantics only affect targets built with the specified toolset,
|
|
and depend on the target's build configuration:</p>
|
|
|
|
<ol>
|
|
<li>if any specified property-set is a subset of the target's build
|
|
properties, the <i>values</i> specified in <tt>$(3)</tt> will be
|
|
appended once to <i>variable</i>.</li>
|
|
|
|
<li>The value of each specified feature that participates in the
|
|
target's build properties is appended to <i>variable</i>. In either
|
|
case, the variable will be set "on" the target so it may be used in
|
|
the build actions.</li>
|
|
</ol>
|
|
</li>
|
|
</ol>
|
|
|
|
<h4><a name="toolset_example">Example</a></h4>
|
|
|
|
<p>The description of the <tt>flags</tt> rule above is actually more
|
|
complicated than it sounds. For example, the following line might be used
|
|
to specify how optimization can be turned off for MSVC:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
flags msvc CFLAGS <optimization>off : /Od ;
|
|
</pre>
|
|
</blockquote>
|
|
It says that the string <tt>/Od</tt> should be added to the global
|
|
<tt>CFLAGS</tt> variable whenever a build configuration includes the
|
|
property <tt><optimization>off</tt>.
|
|
|
|
<p>Similarly, in the following example,</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
flags msvc CFLAGS <runtime-build>release/<runtime-link>dynamic : /MD ;
|
|
</pre>
|
|
</blockquote>
|
|
we add <tt>/MD</tt> to the CFLAGS variable when both of the specified
|
|
conditions are satisfied. We could grab all of the values of the free
|
|
feature <tt><include></tt> in the <tt>HDRS</tt> variable as
|
|
follows:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
flags msvc HDRS <include> ;
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p>The use of these variables should be apparent from the declaration of
|
|
<tt>actions msvc-C++-action</tt> in the previous section.</p>
|
|
|
|
<h2><a name="internals">Internals</a></h2>
|
|
|
|
<h3><a name="jam_fundamentals">Jam Fundamentals</a></h3>
|
|
|
|
<p>This section is derived from the official Jam documentation and from
|
|
my experience using it and reading the Jambase rules. I repeat the
|
|
information here mostly because it is essential to understanding and
|
|
using Jam, but is not consolidated in a single place. Some of it is
|
|
missing from the official documentation altogether. I hope it will be
|
|
useful to anyone wishing to become familiar with Jam and the Boost build
|
|
system.</p>
|
|
|
|
<ul>
|
|
<li>Jam ``<b>rules</b>'' are actually simple procedural entities. Think
|
|
of them as functions. Arguments are separated by colons.</li>
|
|
|
|
<li>A Jam <b>target</b> is an abstract entity identified by an
|
|
arbitrary string. The build-in <tt>DEPENDS</tt> rule creates a link in
|
|
the dependency graph between the named targets.</li>
|
|
|
|
<li>Note that the documentation for the built-in <tt>INCLUDES</tt> rule
|
|
is incorrect: <tt>INCLUDES targets1 : targets2</tt>
|
|
causes everything that depends on a member of <i>targets1</i> to depend
|
|
on all members of <i>targets2</i>. It does this in an odd way, by
|
|
tacking <i>targets2</i> onto a special tail section in the dependency
|
|
list of everything in <i>targets1</i>. It seems to be OK to create
|
|
circular dependencies this way; in fact, it appears to be the ``right
|
|
thing to do'' when a single build action produces both <i>targets1</i>
|
|
and <i>targets2</i>.</li>
|
|
|
|
<li>When a rule is invoked, if there are <b><tt>actions</tt></b>
|
|
declared with the same name as the rule, the <tt>actions</tt> are added
|
|
to the updating actions for the target identified by the rule's first
|
|
argument. It is actually possible to invoke an undeclared rule if
|
|
corresponding actions are declared: the rule is treated as empty.</li>
|
|
|
|
<li><a name="binding">Targets</a> (other than <tt>NOTFILE</tt> targets)
|
|
are associated with paths in the file system through a process called
|
|
<a href=
|
|
"http://public.perforce.com/public/jam/src/Jam.html#binding">binding</a>.
|
|
Binding is a process of searching for a file with the same name as the
|
|
target (sans <a href="#grist">grist</a>), based on the settings of the
|
|
<a href="#target_specific">target-specific</a> <tt>SEARCH</tt> and
|
|
<tt>LOCATE</tt> variables.</li>
|
|
|
|
<li>
|
|
<a name="target_specific">In addition to</a> local and global
|
|
variables, jam allows you to set a variable <tt><b>on</b></tt> a
|
|
target. Target-specific variable values can usually not be read, and
|
|
take effect <i>only</i> in the following contexts:
|
|
|
|
<ul>
|
|
<li>In updating <tt>actions</tt>, variable values are first looked
|
|
up <tt><b>on</b></tt> the target named by the first argument (the
|
|
target being updated). Because Jam builds its entire dependency
|
|
tree before executing <tt>actions</tt>, Jam rules make
|
|
target-specific variable settings as a way of supplying parameters
|
|
to the corresponding <tt>actions</tt>.</li>
|
|
|
|
<li>Binding is controlled <i>entirely</i> by the target-specific
|
|
setting of the <tt>SEARCH</tt> and <tt>LOCATE</tt> variables, as
|
|
described <a href=
|
|
"http://public.perforce.com/public/jam/src/Jam.html#search">here</a>.</li>
|
|
|
|
<li>In the special rule used for <a href=
|
|
"http://public.perforce.com/public/jam/src/Jam.html#hdrscan">header
|
|
file scanning</a>, variable values are first looked up
|
|
<tt><b>on</b></tt> the target named by the rule's first argument
|
|
(the source file being scanned).</li>
|
|
</ul>
|
|
</li>
|
|
|
|
<li>The ``<b>bound value</b>'' of a variable is the path associated
|
|
with the target named by the variable. In build <tt>actions</tt>, the
|
|
first two arguments are automatically replaced with their bound values.
|
|
Target-specific variables can be selectively replaced by their bound
|
|
values using the <a href=
|
|
"http://public.perforce.com/public/jam/src/Jam.html#actionmods">bind</a>
|
|
action modifier.</li>
|
|
|
|
<li>Note that the term ``binding'' as used in the Jam documentation
|
|
indicates a phase of processing that includes three sub-phases:
|
|
<i>binding</i> (yes!), update determination, and header file scanning.
|
|
The repetition of the term ``binding'' can lead to some confusion. In
|
|
particular, the <a href=
|
|
"http://public.perforce.com/public/jam/src/Jam.html#bindingmods">Modifying
|
|
Binding</a> section in the Jam documentation should probably be titled
|
|
``Modifying Update Determination''.</li>
|
|
|
|
<li>
|
|
<p>``<a href="#grist">Grist</a>'' is just a string prefix of the form
|
|
<tt><</tt><i>characters</i><tt>></tt>. It is used in Jam to
|
|
create unique target names based on simpler names. For example, the
|
|
file name ``<tt>test.exe</tt>'' may be used by targets in separate
|
|
subprojects, or for the debug and release variants of the ``same''
|
|
abstract target. Each distinct target bound to a file called
|
|
``<tt>test.exe</tt>'' has its own unique grist prefix. The Boost
|
|
build system also takes full advantage of Jam's ability to divide
|
|
strings on grist boundaries, sometimes concatenating multiple gristed
|
|
elements at the beginning of a string. Grist is used instead of
|
|
identifying targets with absolute paths for two reasons:</p>
|
|
|
|
<ol summary="">
|
|
<li>The location of targets cannot always be derived solely from
|
|
what the user puts in a Jamfile, but sometimes depends also on the
|
|
<a href="#binding">binding</a> process. Some mechanism to
|
|
distinctly identify targets with the same name is still
|
|
needed.</li>
|
|
|
|
<li>Grist allows us to use a uniform abstract identifier for each
|
|
built target, regardless of target file location (as allowed by
|
|
setting <tt>ALL_LOCATE_TARGET</tt>.</li>
|
|
</ol>
|
|
When grist is extracted from a name with
|
|
<tt>$(</tt><i>var</i><tt>:G)</tt>, the result includes the leading
|
|
and trailing angle brackets. When grist is added to a name with
|
|
<tt>$(</tt><i>var</i><tt>:G=</tt><i>expr</i><tt>)</tt>, existing
|
|
grist is first stripped. Then, if <i>expr</i> is non-empty, leading
|
|
<tt><</tt>s and trailing <tt>></tt>s are added if necessary to
|
|
form an expression of the form
|
|
<tt><</tt><i>expr2</i><tt>></tt>;
|
|
<tt><</tt><i>expr2</i><tt>></tt> is then prepended.
|
|
</li>
|
|
|
|
<li><a name="variable_splitting">When Jam</a> is invoked it imports all
|
|
environment variable settings into corresponding Jam variables,
|
|
followed by all command-line (<tt>-s...</tt>) variable settings.
|
|
Variables whose name ends in <tt>PATH</tt>, <tt>Path</tt>, or
|
|
<tt>path</tt> are split into string lists on OS-specific path-list
|
|
separator boundaries (e.g. "<tt>:</tt>" for UNIX and "<tt>;</tt>" for
|
|
Windows). All other variables are split on space ("<tt> </tt>")
|
|
boundaries. Boost Jam modifies that behavior by allowing variables to
|
|
be <a href="#variable_quoting">quoted</a>.</li>
|
|
|
|
<li>
|
|
A variable whose value is an empty list <i>or</i> which consists
|
|
entirely of empty strings has a negative logical value. Thus, for
|
|
example, code like the following allows a sensible non-empty default
|
|
which can easily be overridden by the user:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
MESSAGE ?= starting jam... ;
|
|
if $(MESSAGE) { ECHO The message is: $(MESSAGE) ; }
|
|
</pre>
|
|
</blockquote>
|
|
If the user wants a specific message, he invokes jam with
|
|
<tt>"-sMESSAGE=</tt><i>message text</i><tt>"</tt>. If he wants
|
|
no message, he invokes jam with <tt>-sMESSAGE=</tt> and nothing at
|
|
all is printed.
|
|
</li>
|
|
</ul>
|
|
|
|
<p>Please also read <a href=
|
|
"http://public.perforce.com/public/jam/src/Jam.html">The Jam language
|
|
reference</a> for the additional details, and the <a href=
|
|
"http://public.perforce.com/public/jam/src/RELNOTES">Jam release
|
|
notes</a> for a brief description of recent, but <b>fundamental changes
|
|
to the Jam language</b> without which you will probably not understand
|
|
any of the build system code. In particular, note that the
|
|
<tt>return</tt> statement does not affect control flow.</p>
|
|
|
|
<h3><a name="core_extensions">Core Jam Extensions</a></h3>
|
|
|
|
<p>A number of enhancements have been made to the core language of
|
|
Classic Jam. These changes were aimed primarily at making it easier to
|
|
manage the complexity of a large system such as Boost.Build.</p>
|
|
|
|
<blockquote>
|
|
<h4><a name="variable_quoting"></a>Command-line and Environment
|
|
Variable Quoting</h4>
|
|
|
|
<p>Classic Jam had an <a href="#variable_splitting">odd behavior</a>
|
|
with respect to command-line variable ( <tt>-s...</tt>) and environment
|
|
variable settings which made it impossible to define an arbitrary
|
|
variable with spaces in the value. Boost Jam remedies that by treating
|
|
all such settings as a single string if they are surrounded by
|
|
double-quotes. Uses of this feature can look interesting, since shells
|
|
require quotes to keep characters separated by whitespace from being
|
|
treated as separate arguments:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
jam -sMSVCNT="\"\"C:\Program Files\Microsoft Visual C++\VC98\"\"" ...
|
|
</pre>
|
|
</blockquote>
|
|
The outer quote is for the shell. The middle quote is for Jam, to tell
|
|
it to take everything within those quotes literally, and the inner
|
|
quotes are for the shell again when paths are passed as arguments to
|
|
build actions. Under NT, it looks a lot more sane to use environment
|
|
variables before invoking jam when you have to do this sort of quoting:
|
|
|
|
|
|
<blockquote>
|
|
<pre>
|
|
set MSVCNT=""C:\Program Files\Microsoft Visual C++\VC98\""
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<h4><a name="jambase_replacement">Startup Behavior</a></h4>
|
|
|
|
<p>The Boost.Build v2 initialization behavior has been implemented.
|
|
This behavior only applies when the executable being invoked is called
|
|
"<code>bjam</code>" or, for backward-compatibility, when the
|
|
<code>BOOST_ROOT</code> variable is set.</p>
|
|
|
|
<ol>
|
|
<li>We attempt to load "boost-build.jam" by searching from the
|
|
current invocation directory up to the root of the file-system. This
|
|
file is expected to invoke the <tt>boost-build</tt> rule to indicate
|
|
where the Boost.Build system files are, and to load them.</li>
|
|
|
|
<li>
|
|
If boost-build.jam is not found we error and exit, giving brief
|
|
instructions on possible errors.
|
|
|
|
<blockquote>
|
|
As a backward-compatibility measure for older versions of
|
|
Boost.Build, when the <code>BOOST_ROOT</code> variable is set, we
|
|
first search for <code>boost-build.jam</code> in
|
|
<code>$(BOOST_ROOT)/tools/build</code> and
|
|
<code>$(BOOST_BUILD_PATH)</code>. If found, it is loaded and
|
|
initialization is complete.
|
|
</blockquote>
|
|
</li>
|
|
|
|
<li>The <code>boost-build</code> rule adds its (optional) argument to
|
|
the front of <code>BOOST_BUILD_PATH</code>, and attempts to load
|
|
<code>bootstrap.jam</code> from those directories. If a relative path
|
|
is specified as an argument, it is treated as though it was relative
|
|
to the <code>boost-build.jam</code> file.</li>
|
|
|
|
<li>If the bootstrap.jam file was not found, we print a likely error
|
|
message and exit.</li>
|
|
</ol>
|
|
|
|
<h4><a name="rule_indirection">Rule Indirection</a></h4>
|
|
|
|
<p>Boost Jam allows you to call a rule whose name is held in a variable
|
|
or computed as the result of an expression:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
x = foo ;
|
|
rule foobar { ECHO foobar ; } # a trivial rule
|
|
$(x)bar ; # invokes foobar
|
|
|
|
</pre>
|
|
</blockquote>
|
|
Furthermore, if the first expression expands to more than one list
|
|
item, everything after the first item becomes part of the first
|
|
argument. This allows a crude form of argument binding:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
# return the elements of sequence for which predicate returns non-nil
|
|
rule filter ( sequence * : predicate + )
|
|
{
|
|
local result ;
|
|
for local x in $(sequence)
|
|
{
|
|
if [ $(predicate) $(x) ] { result += $(x); }
|
|
}
|
|
return $(result);
|
|
}
|
|
|
|
# true iff x == y
|
|
rule equal ( x y )
|
|
{
|
|
if $(x) = $(y) { return true; }
|
|
}
|
|
|
|
# bind 3 to the first argument of equal
|
|
ECHO [ filter 1 2 3 4 5 4 3 : equal 3 ] ; # prints "3 3"
|
|
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<h4><a name="argument_lists">Argument lists</a></h4>
|
|
|
|
<p>You can now describe the arguments accepted by a rule, and refer to
|
|
them by name within the rule. For example, the following prints ``I'm
|
|
sorry, Dave'' to the console:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule report ( pronoun index ? : state : names + )
|
|
{
|
|
local he.suffix she.suffix it.suffix = s ;
|
|
local I.suffix = m ;
|
|
local they.suffix you.suffix = re ;
|
|
|
|
ECHO $(pronoun)'$($(pronoun).suffix) $(state), $(names[$(index)]) ;
|
|
}
|
|
report I 2 : sorry : Joe Dave Pete ;
|
|
</pre>
|
|
</blockquote>
|
|
Each name in a list of formal arguments (separated by ``<tt>:</tt>'' in
|
|
the rule declaration) is bound to a single element of the corresponding
|
|
actual argument unless followed by one of these modifiers:
|
|
|
|
<table border="1" summary="Argument modifiers">
|
|
<tr>
|
|
<th>Symbol</th>
|
|
|
|
<th>Semantics of preceding symbol</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><tt>?</tt></td>
|
|
|
|
<td>optional</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><tt>*</tt></td>
|
|
|
|
<td>Bind to zero or more unbound elements of the actual argument.
|
|
When ``<tt>*</tt>'' appears where an argument name is expected, any
|
|
number of additional arguments are accepted. This feature can be
|
|
used to implement "varargs" rules.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><tt>+</tt></td>
|
|
|
|
<td>Bind to one or more unbound elements of the actual
|
|
argument.</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<p>The actual and formal arguments are checked for inconsistencies,
|
|
which cause Jam to exit with an error code:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
### argument error
|
|
# rule report ( pronoun index ? : state : names + )
|
|
# called with: ( I 2 foo : sorry : Joe Dave Pete )
|
|
# extra argument foo
|
|
|
|
### argument error
|
|
# rule report ( pronoun index ? : state : names + )
|
|
# called with: ( I 2 : sorry )
|
|
# missing argument names
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p>If you omit the list of formal arguments, all checking is bypassed
|
|
as in ``classic'' Jam. Argument lists drastically improve the
|
|
reliability and readability of your rules, however, and are <b>strongly
|
|
recommended</b> for any new Jam code you write.</p>
|
|
|
|
<h4><a name="module_support">Module Support</a></h4>
|
|
|
|
<p>Boost Jam introduces support for modules, which provide some
|
|
rudimentary namespace protection for rules and variables. A new
|
|
keyword, ``<tt>module</tt>'' was also introduced. The features
|
|
described in this section are <i>primitives</i>, meaning that they are
|
|
meant to provide the operations needed to write Jam rules which provide
|
|
a more elegant module interface.</p>
|
|
|
|
<blockquote>
|
|
<h5>Declaration</h5>
|
|
<a name="module_declaration"><tt>module </tt>
|
|
<i>expression</i><tt> { </tt> ...<tt> } </tt></a>
|
|
|
|
|
|
<p>Code within the <tt>{ </tt> ...<tt> }</tt> executes
|
|
within the module named by evaluating <i>expression</i>. Rule
|
|
definitions can be found in the module's own namespace, and in the
|
|
namespace of the global module as
|
|
<i>module-name</i><tt>.</tt><i>rule-name</i>, so within a module,
|
|
other rules in that module may always be invoked without
|
|
qualification:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
<b>module my_module
|
|
{</b>
|
|
rule salute ( x ) { ECHO $(x), world ; }
|
|
rule greet ( ) { salute hello ; }
|
|
greet ;
|
|
<b>}
|
|
my_module.salute</b> goodbye ;
|
|
</pre>
|
|
</blockquote>
|
|
When an invoked rule is not found in the current module's namespace,
|
|
it is looked up in the namespace of the global module, so qualified
|
|
calls work across modules:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
module your_module
|
|
{
|
|
rule bedtime ( ) { <b>my_module.salute</b> goodnight ; }
|
|
}
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<h5><a name="module_locals">Variable Scope</a></h5>
|
|
|
|
<p>Each module has its own set of dynamically nested variable scopes.
|
|
When execution passes from module A to module B, all the variable
|
|
bindings from A become unavailable, and are replaced by the bindings
|
|
that belong to B. This applies equally to local and global
|
|
variables:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
module A
|
|
{
|
|
x = 1 ;
|
|
rule f ( )
|
|
{
|
|
local y = 999 ; # becomes visible again when B.f calls A.g
|
|
B.f ;
|
|
}
|
|
rule g ( )
|
|
{
|
|
ECHO $(y) ; # prints "999"
|
|
}
|
|
}
|
|
|
|
module B
|
|
{
|
|
y = 2 ;
|
|
rule f ( )
|
|
{
|
|
ECHO $(y) ; # always prints "2"
|
|
A.g ;
|
|
}
|
|
}
|
|
</pre>
|
|
</blockquote>
|
|
The only way to access another module's variables is by entering that
|
|
module:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule peek ( module-name ? : variables + )
|
|
{
|
|
module $(module-name)
|
|
{
|
|
return $($(>)) ;
|
|
}
|
|
}
|
|
</pre>
|
|
</blockquote>
|
|
Note that because existing variable bindings change whenever a new
|
|
module scope is entered, argument bindings become unavailable. That
|
|
explains the use of "<code>$(>)</code>" in the <code>peek</code>
|
|
rule above.
|
|
|
|
<h5><a name="local_rules">Local Rules</a></h5>
|
|
|
|
<blockquote>
|
|
<tt>local rule</tt> <i>rulename...</i>
|
|
</blockquote>
|
|
|
|
<p>The rule is declared locally to the current module. It is not
|
|
entered in the global module with qualification, and its name will
|
|
not appear in the result of</p>
|
|
|
|
<blockquote>
|
|
<tt>[ RULENAMES</tt> <i>module-name</i><tt> ]</tt>.
|
|
</blockquote>
|
|
|
|
<h5><a name="RULENAMES_rule">The <tt>RULENAMES</tt> Rule</a></h5>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule RULENAMES ( module ? )
|
|
</pre>
|
|
</blockquote>
|
|
Returns a list of the names of all non-local rules in the given
|
|
module. If <tt>module</tt> is omitted, the names of all non-local
|
|
rules in the global module are returned.
|
|
|
|
<h5><a name="IMPORT_rule">The <tt>IMPORT</tt> Rule</a></h5>
|
|
<tt>IMPORT</tt> allows rule name aliasing across modules:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule IMPORT ( source_module ? : source_rules *
|
|
: target_module ? : target_rules * )
|
|
</pre>
|
|
</blockquote>
|
|
The <tt>IMPORT</tt> rule copies rules from the <tt>source_module</tt>
|
|
into the <tt>target_module</tt> as <tt>local</tt> rules. If either
|
|
<tt>source_module</tt> or <tt>target_module</tt> is not supplied, it
|
|
refers to the global module. <tt>source_rules</tt> specifies which
|
|
rules from the <tt>source_module</tt> to import;
|
|
<tt>TARGET_RULES</tt> specifies the names to give those rules in
|
|
<tt>target_module</tt>. If <tt>source_rules</tt> contains a name
|
|
which doesn't correspond to a rule in <tt>source_module</tt>, or if
|
|
it contains a different number of items than <tt>target_rules</tt>,
|
|
an error is issued. For example,
|
|
|
|
<blockquote>
|
|
<pre>
|
|
# import m1.rule1 into m2 as local rule m1-rule1.
|
|
IMPORT m1 : rule1 : m2 : m1-rule1 ;
|
|
|
|
# import all non-local rules from m1 into m2
|
|
IMPORT m1 : [ RULENAMES m1 ] : m2 : [ RULENAMES m1 ] ;
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<h5><a name="EXPORT_rule">The <tt>EXPORT</tt> Rule</a></h5>
|
|
<tt>EXPORT</tt> allows rule name aliasing across modules:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule EXPORT ( module ? : rules * )
|
|
</pre>
|
|
</blockquote>
|
|
The <tt>EXPORT</tt> rule marks <tt>rules</tt> from the
|
|
<tt>source_module</tt> as non-local (and thus exportable). If an
|
|
element of <tt>rules</tt> does not name a rule in <tt>module</tt>, an
|
|
error is issued. For example,
|
|
|
|
<blockquote>
|
|
<pre>
|
|
module X {
|
|
local rule r { ECHO X.r ; }
|
|
}
|
|
IMPORT X : r : : r ; # error - r is local in X
|
|
EXPORT X : r ;
|
|
IMPORT X : r : : r ; # OK.
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<h5><a name="CALLER_MODULE_rule">The <tt>CALLER_MODULE</tt>
|
|
Rule</a></h5>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule CALLER_MODULE ( levels ? )
|
|
</pre>
|
|
</blockquote>
|
|
<tt>CALLER_MODULE</tt> returns the name of the module scope enclosing
|
|
the call to its caller (if levels is supplied, it is interpreted as
|
|
an integer number of additional levels of call stack to traverse to
|
|
locate the module). If the scope belongs to the global module, or if
|
|
no such module exists, returns the empty list. For example, the
|
|
following prints "{Y} {X}":
|
|
|
|
<blockquote>
|
|
<pre>
|
|
module X {
|
|
rule get-caller { return [ CALLER_MODULE ] ; }
|
|
rule get-caller's-caller { return [ CALLER_MODULE 1 ] ; }
|
|
|
|
rule call-Y { return Y.call-X2 ; }
|
|
|
|
}
|
|
module Y {
|
|
rule call-X { return X.get-caller ; }
|
|
rule call-X2 { return X.get-caller's-caller ; }
|
|
}
|
|
|
|
callers = [ X.get-caller ] [ Y.call-X ] [ X.call-Y ] ;
|
|
ECHO {$(callers)} ;
|
|
|
|
</pre>
|
|
</blockquote>
|
|
</blockquote>
|
|
|
|
<h4><a name="local_foreach">Local For Loop Variables</a></h4>
|
|
|
|
<p>Boost Jam allows you to declare a local <tt>for</tt> loop control
|
|
variable right in the loop:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
x = 1 2 3 ;
|
|
y = 4 5 6 ;
|
|
for <b>local</b> y in $(x)
|
|
{
|
|
ECHO $(y) ; # prints "1", "2", or "3"
|
|
}
|
|
ECHO $(y) ; # prints "4 5 6"
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<h4><a name="negative_indexing">Negative Indexing</a></h4>
|
|
Classic Jam supplies 1-based list indexing, and slicing on a closed
|
|
(inclusive) range:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
x = 1 2 3 4 5 ;
|
|
ECHO $(x[3]) ; # prints "3"
|
|
ECHO $(x[2-4]) ; # prints "2 3 4"
|
|
ECHO $(x[2-]) ; # prints "2 3 4 5"
|
|
</pre>
|
|
</blockquote>
|
|
Boost Jam adds Python-style negative indexing to access locations
|
|
relative to the <i>end</i> of the list.
|
|
|
|
<blockquote>
|
|
<pre>
|
|
ECHO $(x[-1]) $(x[-3]) ; # prints "5 3"
|
|
ECHO $(x[-3--1]) ; # prints "3 4 5"
|
|
ECHO $(x[-3-4]) ; # prints "3 4"
|
|
ECHO $(x[2--2]) ; # prints "2 3 4"
|
|
</pre>
|
|
</blockquote>
|
|
Consistency with the 1-based, inclusive indexing of Classic Jam and the
|
|
use of ``<tt>-</tt>'' as the range separator make this feature a bit
|
|
clumsier than it would otherwise need to be, but it does work.
|
|
|
|
<h4><a name="BINDRULE">Target Binding Detection</a></h4>
|
|
|
|
<p>Whenever a target is <a href="#binding">bound</a> to a location in
|
|
the filesystem, Boost Jam will look for a variable called
|
|
<tt>BINDRULE</tt> (first ``<tt>on</tt>'' the target being bound, then
|
|
in the global module). If non-empty, <tt>$(BINDRULE[1])</tt> names a
|
|
rule which is called with the name of the target and the path it is
|
|
being bound to. The signature of the rule named by
|
|
<tt>$(BINDRULE[1])</tt> should match the following:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule bind-rule ( target : path )
|
|
</pre>
|
|
</blockquote>
|
|
This facility is useful for correct header file scanning, since many
|
|
compilers will search for <tt>#include</tt>d files first in the
|
|
directory containing the file doing the <tt>#include</tt> directive.
|
|
<tt>$(BINDRULE)</tt> can be used to make a record of that directory.
|
|
|
|
<h4><a name="FAIL_EXPECTED">Return Code Inversion</a></h4>
|
|
|
|
<p>For handling targets whose build actions are expected to fail (e.g.
|
|
when testing that assertions or compile-time type checkin work
|
|
properly), Boost Jam supplies a <tt>FAIL_EXPECTED</tt> rule in the same
|
|
style as <tt>NOCARE</tt>, et. al. During target updating, the return
|
|
code of the build actions for arguments to <tt>FAIL_EXPECTED</tt> is
|
|
inverted: if it fails, building of dependent targets continues as
|
|
though it succeeded. If it succeeds, dependent targets are skipped.</p>
|
|
|
|
<h4><a name="NOCARE">Ignoring Return Codes</a></h4>
|
|
|
|
<p>Perforce Jam supplied a <tt>NOCARE</tt> rule which is typically used
|
|
for header files to indicate that if they are not found, the dependent
|
|
targets should be built anyway. Boost Jam extends <tt>NOCARE</tt> to
|
|
apply to targets with build actions: if their build actions exit with a
|
|
nonzero return code, dependent targets will still be built.</p>
|
|
|
|
<h4><a name="RMOLD">Removing Outdated Targets</a></h4>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule RMOLD ( targets * )
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p>Perforce Jam removes any target files that may exist on disk when
|
|
the rule used to build those targets fails. However, targets whose
|
|
dependencies fail to build are not removed by default. The
|
|
<code>RMOLD</code> rule causes its arguments to be removed if any of
|
|
their dependencies fail to build.</p>
|
|
|
|
<h4><a name="SUBST_rule">The <tt>SUBST</tt> Rule</a></h4>
|
|
|
|
<p><b>Note:</b> the <code>SUBST</code> rule is deprecated in favor of
|
|
Perforce Jam's built-in <code>MATCH</code> rule, which has been rolled
|
|
into Boost.Jam.</p>
|
|
|
|
<p>The behavior of the <tt>SUBST</tt> rule for regular-expression
|
|
matching and replacement (originally added in <a href=
|
|
"http://freetype.sourceforge.net/jam/index.html">FTJam</a>) has been
|
|
modified:</p>
|
|
|
|
<ul>
|
|
<li>
|
|
One or more replacement patterns may be supplied. The new signature
|
|
for <tt>SUBST</tt> is:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
SUBST ( source pattern replacements + )
|
|
</pre>
|
|
</blockquote>
|
|
The return value is the concatenated results of applying each
|
|
element of <tt>replacements</tt> in turn. For example, the
|
|
following will print ``<tt>[x] (y) {z}</tt>'':
|
|
|
|
<blockquote>
|
|
<pre>
|
|
ECHO [ SUBST xyz (.)(.)(.) [$1] ($2) {$3} ] ;
|
|
</pre>
|
|
</blockquote>
|
|
</li>
|
|
|
|
<li>If there is no match, <tt>SUBST</tt> now returns an empty list.
|
|
In FTJam, the original <tt>source</tt> string was returned, making it
|
|
awkward to check whether a pattern was matched.</li>
|
|
|
|
<li>Compiled regular expressions are now internally cached, making it
|
|
much faster to use <tt>SUBST</tt> multiple times with the same
|
|
string.</li>
|
|
</ul>
|
|
|
|
<h4><a name="#JAM_VERSION">The <tt>JAM_VERSION</tt> global
|
|
variable</a></h4>
|
|
|
|
<p>A predefined global variable with two elements indicates the version
|
|
number of Boost Jam. Boost Jam versions start at <tt>"03" "00"</tt>.
|
|
Earlier versions of Jam do not automatically define
|
|
<tt>JAM_VERSION</tt>.</p>
|
|
|
|
<h4><a name="debugging_support">Debugging Support</a></h4>
|
|
|
|
<h5><a name="BACKTRACE_rule">The BACKTRACE rule</a></h5>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule BACKTRACE ( )
|
|
</pre>
|
|
</blockquote>
|
|
Returns a list of quadruples: <i>filename line module rulename</i>...,
|
|
describing each shallower level of the call stack. This rule can be
|
|
used to generate useful diagnostic messages from Jam rules.
|
|
|
|
<p>The <tt>-d</tt> command-line option admits new arguments:</p>
|
|
|
|
<ul>
|
|
<li><tt>-d+10</tt> - enables <a name="profiling"><b>profiling</b></a>
|
|
of rule invocations. When Jam exits, it dumps all rules invoked,
|
|
their gross and net times in platform-dependent units, and the number
|
|
of times the rule was invoked.</li>
|
|
|
|
<li><tt>-d+11</tt> - enables <a name="parse_debugging"><b>parser
|
|
debugging</b></a>, if Jam has been compiled with the "--debug" option
|
|
to the parser generator named by $(YACC).</li>
|
|
|
|
<li><tt>-d+12</tt> - enables <a name="dependency_graph"><b>dependency
|
|
graph output</b></a> . This feature was ``stolen'' from a version of
|
|
Jam modified by <a href="mailto:cmcpheeters@aw.sgi.com">Craig
|
|
McPheeters</a>.</li>
|
|
</ul>
|
|
</blockquote>
|
|
|
|
<h4><a name="UPDATE">The <tt>UPDATE</tt> rule and changes to command line
|
|
handling</a></h4>
|
|
|
|
<p>Classic jam treats any non-option element of command line as a name of
|
|
target to be updated. This prevented more sophisticated handling of
|
|
command line and was disabled. Instead of it, a new <tt>UPDATE</tt>
|
|
builtin rule was added:</p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
rule UPDATE ( targets * )
|
|
</pre>
|
|
</blockquote>
|
|
The rule causes the specified targets to be updated. If no target was
|
|
specified with the <tt>UPDATE</tt> rule, the "all" target will be
|
|
implicitly updated.
|
|
|
|
<h3><a name="target_names">Target Names</a></h3>
|
|
|
|
<p>In addition to <a href="#user_targets">user targets</a>, which
|
|
correspond directly to the names the user writes in her subproject
|
|
Jamfile, several additional targets are generated, regardless of the
|
|
directory from which Jam was invoked:</p>
|
|
|
|
<ul>
|
|
<li>A <b>main target</b> has all the same dependencies as a user target
|
|
(i.e. building it updates all requested subvariants). Its name is the
|
|
same except for the addition of <tt>$(SOURCE_GRIST)</tt>, which
|
|
identifies the subproject. The identification looks like the names of
|
|
the path components from the project root to the subproject, separated
|
|
by exclamation points. Thus, if the project is rooted at <tt>foo</tt>,
|
|
in the subproject at <tt>foo/bar/baz</tt> the target <tt>my_target</tt>
|
|
is identified by <tt><bar!baz>my_target</tt>.</li>
|
|
|
|
<li>A <b>subvariant target</b> has additional grist identifying its
|
|
main target and subvariant. This grist is joined to
|
|
<tt>$(SOURCE_GRIST)</tt> with the platform's directory separator. Thus,
|
|
on UNIX, a subvariant target of <tt>my_target</tt> above might be
|
|
identified as
|
|
<tt><bar!baz/my_target/optimization-space/runtime-link-static>my_source.o</tt>.
|
|
Note that the part of the grist following the first slash, known as the
|
|
<b>subvariant id</b>, also corresponds to a fragment of the subvariant
|
|
directory path where the corresponding target is generated. Most built
|
|
targets will be identified this way.</li>
|
|
</ul>
|
|
|
|
<h3><a name="internal_globals">Global Variables</a></h3>
|
|
|
|
<p>This section describes some of the global variables used by the build
|
|
system. Please note that some parts of the system (particularly those in
|
|
<tt>allyourbase.jam</tt>) are heavily based on the Jambase file supplied
|
|
with Jam, and as such do not follow the conventions described below.</p>
|
|
|
|
<p>Global variables used in the build system fall into three
|
|
categories:</p>
|
|
|
|
<ul>
|
|
<li>Global variables intended to be set by the user on the command-line
|
|
or in the environment use <tt>ALL_UPPER_CASE</tt> names.</li>
|
|
|
|
<li>Internal global variables begin with a lower-case "g" and continue
|
|
in upper-case: <tt>gSOME_GLOBAL</tt></li>
|
|
|
|
<li>
|
|
Global variables of the form:
|
|
<tt>gBASE_NAME(</tt><i>arguments</i><tt>)</tt>, where
|
|
<i>arguments</i> is a comma-separated argument list, are used
|
|
internally to achieve a kind of indirection by concatenating variable
|
|
values:
|
|
|
|
<blockquote>
|
|
<pre>
|
|
ECHO $(gFUBAR($(x),$(y))) ;
|
|
</pre>
|
|
</blockquote>
|
|
</li>
|
|
</ul>
|
|
|
|
<p>Please note that the build system commonly takes advantage of <a href=
|
|
"http://public.perforce.com/public/jam/src/Jam.html#bindingmods">Jam's
|
|
Dynamic Scoping feature</a> (see the <tt>local</tt> command in the "Flow
|
|
of Control" section below the link target) to temporarily "change" a
|
|
global variable by declaring a <tt>local</tt> of the same name.</p>
|
|
|
|
<p>Many of the variables that are used to configure how Boost.Build works
|
|
internally are listed <a href="variables.html">here</a> with brief
|
|
descriptions.</p>
|
|
|
|
<h3>Variables Associated with SubProject Identity</h3>
|
|
|
|
<ul>
|
|
<li><tt>SUBDIR_TOKENS</tt> - a list of the path elements relative to
|
|
the project root of the current subproject.</li>
|
|
|
|
<li><tt>SUBDIR</tt> - the path from the invocation directory to the
|
|
current subproject directory.</li>
|
|
</ul>
|
|
|
|
<h3>Grist Variables</h3>
|
|
|
|
<ul>
|
|
<li><tt>TARGET_GRIST</tt> takes the form
|
|
<tt><i>subproject!id</i>/target/toolset/variant/<i>subvariant-path</i></tt>.</li>
|
|
</ul>
|
|
|
|
<h2><a name="design_criteria">Design Criteria</a></h2>
|
|
|
|
<h3><a name="assumptions">Assumptions</a></h3>
|
|
|
|
<p>The requirements are driven by several basic assumptions:</p>
|
|
|
|
<ul>
|
|
<li>There is no single Boost developer or test facility with access to
|
|
or knowledge of all the platforms and compilers Boost libraries are
|
|
used with.</li>
|
|
|
|
<li>Boost libraries are used across such a wide range of platforms and
|
|
compilers that almost no other assumptions can be made.</li>
|
|
</ul>
|
|
|
|
<h3><a name="requirements">Requirements</a></h3>
|
|
|
|
<p>This build system was designed to satisfy the following
|
|
requirements:</p>
|
|
|
|
<ul>
|
|
<li>A developer adding a new library or test program must only have to
|
|
add simple entries naming the source files to a text file, and not have
|
|
to know anything about platform specific files. The developer should
|
|
not have to supply header dependency information.</li>
|
|
|
|
<li>There should be a very high likelihood of builds succeeding on all
|
|
platforms if a build succeeds on any platform. In other words, a
|
|
developer must not be required to have access to many platforms or
|
|
compilers to ensure correct builds</li>
|
|
|
|
<li>A user or developer adding support for a new platform or compiler
|
|
should only have to add to a single file describing how to do the build
|
|
for that platform or compiler, and shouldn't have to identify the files
|
|
that will need to be built.</li>
|
|
|
|
<li>The build should rely only on tools native to the platform and
|
|
compiler, or supplied via the boost download.</li>
|
|
|
|
<li>The details of how the build is done for a particular platform or
|
|
compiler should be appropriate for that platform.</li>
|
|
|
|
<li>It should be possible to build multiple variants (e.g.
|
|
debug/release) of a single target.</li>
|
|
|
|
<li>It should be possible to build multiple variants of multiple
|
|
targets with multiple compilers from a single build command.</li>
|
|
|
|
<li>The build tools must be able to handle Boost growth issues such as
|
|
identified in Directory Structure proposals and discussion.</li>
|
|
|
|
<li>Support for dynamic and static linking should be included.</li>
|
|
|
|
<li>It should be relatively straightforward to add support for a new
|
|
compiler. In most cases, no modification of files used to describe
|
|
existing targets should be required.</li>
|
|
|
|
<li>Support for compiler- and variant-specific configuration for each
|
|
target</li>
|
|
|
|
<li>It should be possible to build targets into a directory unrelated
|
|
to the source directories (they may be read-only)</li>
|
|
</ul>
|
|
|
|
<h2><a name="footnotes">Footnotes</a></h2>
|
|
<a name="1">[1]</a> Boost Jam is actually descended directly from <a
|
|
href="http://freetype.sourceforge.net/jam/index.html">FTJam</a>, which
|
|
was itself a variant of <a href=
|
|
"http://www.perforce.com/jam/jam.html">Jam/MR</a>. It is hoped that
|
|
crucial features we rely on will eventually be incorporated back into the
|
|
Jam/MR release.
|
|
|
|
<p><a name="2">[2]</a> Note: right now, a dependency feature of a main
|
|
target makes <b>all</b> resulting built targets dependent, including
|
|
intermediate targets. That means that if an executable is dependent on an
|
|
external library, and that library changes, all the sources comprising
|
|
the executable will be recompiled as well. This behavior should probably
|
|
be fixed.</p>
|
|
<hr>
|
|
|
|
<p>© Copyright David Abrahams 2001. Permission to copy, use, modify,
|
|
sell and distribute this document is granted provided this copyright
|
|
notice appears in all copies. This document is provided "as is" without
|
|
express or implied warranty, and with no claim as to its suitability for
|
|
any purpose.</p>
|
|
|
|
<p>Revised
|
|
<!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan
|
|
-->24 May, 2002
|
|
<!--webbot bot="Timestamp" endspan i-checksum="13972"
|
|
-->
|
|
</p>
|
|
</body>
|
|
</html>
|
|
|